package Testdmo4;

import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description: 100 以内的总和
 * User:周次煜
 * Date: 2024-03-15
 * Time：10:49
 */
public class Test2 {
    public  static  int sum(int x) {
        if (x==1) {
            return 1;
        }
        return x+sum(x-1);
    }

    public static void main(String[] args) {
        Scanner s=new Scanner(System.in);
        int n=s.nextInt();
        int ret=sum(n);
        System.out.println(ret);
    }

}
